This invention relates to presses, in particular to large, up to 500 kiloton, forging presses and is specifically directed to novel tie-rod and tie-rod to crosshead coupling configurations for such presses.
By way of background, a forging press is used for shaping metal ingots or slabs into end products of desired shape. In the press the metal slab is gradually pressed between lower and upper dies in the shape of the final end product. In response to the application of extremely high pressures, on the order of 80,000 psi or more, the metal enters a flowable state which enables it to conform to the shape of the dies.
The larger the size of the end product the greater must be the capacity of the press since the total force developed by the press is distributed over the larger area of the end product. It is apparent therefore that press capacity imposes a limit on the dimensions of forged end products.
The largest presses in the United States today are rated at about 50 kilotons. Thus, conventional presses are inadequate for meeting recent needs for larger forged pieces, particularly for satisfying aircraft industry requirements.
The design of any press entails difficult design considerations because of the sheer enormity of presses of this type. Large forging presses will have a steel frame structure, whose size is equivalent to a building several stories in height. For example, in one particular type of forging press known as a pull-down press the frame is moveable up and down relative to a stationary bridge. An upper crosshead of the frame is used for squeezing the workpiece between the frame and the stationary bridge. The enormous operational stresses which develop in the frame must be distributed evenly, under all circumstances, to prevent overstressing and damage to individual components of the press. Moreover, the estimated cost of several hundreds of millions of dollars of a press of this type is not justified unless the components of the press are designed for a long life of at least ten million press stroke cycles.
Forging press components are described in U.S. Pat. Nos. 3,346,922, 2,756,589 and other patents to which one or more of the inventors of the present application have contributed. A basic forging press frame includes two horizontal upper and lower crosshead assemblies and two or more vertical tie-rod assemblies which connect the upper and lower crosshead assemblies to complete the frame. The overall appearance is that of a window or door frame of enormous size, through which extends the stationary bridge on which the work piece is located. There is clearance under the stationary bridge to permit the upper crosshead of the frame to be lowered onto the stationary bridge or to be raised sufficiently above it to create a space which accommodates the workpiece, its dies, etc.
The present invention is concerned with the structure of the frame for a forging press. The frame is usable with either a pull-down forging press or a stationary forging press. Known frame designs are deemed to be inadequate for larger presses which are now in various planning stages. Known frame designs would present insurmountable fabrication problems in light of available steel industry facilities and would not meet required and desired reliability and design life objectives.